Thermal Insulation of Radon Systems to Avoid Freezing

Syracuse, NY

Radon (Rn) stacks, with or without an inline Rn fan, are designed to extract damp soil gas from under basement concrete slabs of homes. Along with Rn gas, moisture vapor also travels up through the Rn stacks. The amount of moisture in the vent pipes can, depending on the circumstances, be significant. In extremely cold weather, this moisture can condense, freeze, form ice and clog the vent pipe at the exit point. In this study, COMSOL Multiphysics was used to examine the amount of insulation required to avoid ice build-up in the Rn vent pipe located in unheated attic space under different outdoor weather conditions. The effects of different parameters on the air temperature in a Rn stack were studied; specifically, (i) air velocities in the vent pipe, (ii) thermal insulations, (iii) different lengths of vent pipe in unheated attic space. The boundary conditions for the model, including the relative humidity, inlet air velocity, and the inlet air temperature in the stack, as well as the temperature in the attic and outdoors were determined based on the data from the Canadian Centre for Housing Technology. Based on the results obtained from numerical simulations, recommendations for insulation to avoid freezing of Rn stack at the exit were proposed. Thereafter, a Rn mitigation system was designed and installed in a home in Ottawa, based on the recommendations. Data was collected from the in-situ experiment during the winter of 2017. This stack was then modeled using the hypothesis used in the predictive simulations, and the model was benchmarked against the data collected from the experiment. The benchmarking results indicated that no freezing was observed using the recommended level of insulation on the Rn vent pipe in an unheated attic and above roof.

https://surface.syr.edu/ibpc/2018/MS3/6